Liquid crystal display elements are now used for the displays of various versions of office automation hardware, inclusive of word processors and laptop computers. They include a liquid crystal layer sandwiched between transparent glass or plastic substrates each having a transparent electrode film, and as voltage is applied between both electrodes using a single or active matrix, they display such information as images. Typical liquid crystal display systems operate in TN, STN, dynamic scattering (operable by current effects) and cholesteric/nematic phase transition modes. A recently developed liquid crystal system, on the other hand, works on a high-molecular/liquid-crystal hybrid mode.
An element having nematic liquid crystals dispersed and fixed in a high-molecular resin system is made transparent by applying voltage thereto with the refractive index of ordinary light through the liquid crystals kept in coincidence with that through the high-molecular resin system, thereby allowing the liquid crystals to line up in the direction of the voltage applied. In the absence of voltage, the liquid crystals do not line up; light incident on the element is scattered on the liquid crystal material/high-molecular resin system interface or through the dispersed and fixed liquid crystal phases, making the element opaque. Thus, this liquid crystal element achieves displays by being made transparent and opaque.
The liquid crystal display element having a nematic type of liquid crystals dispersed and fixed in a high-molecular resin system has advantages of having a large area, a short response, esp., fall time, making effective use of light due to no need of using any polarizer, having a wide and uniform angle of field and being flexible, and so has recently been reported to be well used as window dimming sheets or a projection type of displays. When applied to the projection type of displays or computer displays, their fall time is as short as 1-30 ms and thus advantageous over that of the most commonly used TN or STN type of displays.
Usually, the liquid crystal display element having a nematic type of liquid crystals dispersed and fixed in a high-molecular resin system is used while it is sandwiched between electrodes, and does or does not provide displays by placing the a.c. voltage applied under on-off control. In this case, it has been reported that the voltage vs. light transmittance suffers some hysteresis, giving rise to a transmittance difference between the rise and fall of the a.c. voltage applied. When the a.c. voltage is cut off or in the absence of any voltage, however, the display element is brought back to the initial transmittance or, in other words, the opaque state.
Displaying such information as images is generally achieved by placing the display element sandwiched between matrix electrodes under on-off control per pixel. In addition, it has been put forth to this end to make use of an image-form of patterned electrodes or an image-form of ultraviolet rays which, in this case, are applied to a high-molecular and liquid crystal hybrid film, said high-molecular material being of an ultraviolet setting type, for instance.
On the other hand, cholesteric/nematic phase transition-mode systems are available as display elements having a memory function. Since they are required to be sandwiched between transparent electrodes each having a homeotropic film, the electrodes are required to have a particular structure, correspondingly.
A main object of this invention is to provide an information-recording medium which can make use of a resin system having liquid crystal phases dispersed over and fixed onto an electrode layer to record and store electrostatic information in the form of visible information and reproduce it at any desired time and which can be recycled, if the information recorded on it is erased, as well as to a method of recording and reproducing electrostatic information.